WASHINGTON  The universe is about 13 billion years old, slightly younger than previously believed, according to a study that measured the cooling of the embers in ancient dying stars.

Experts said the finding gives "very comparable results" to an earlier study that used a different method to conclude that the universe burst into existence with the theoretical "Big Bang" between 13 and 14 billion years ago.

Harvey B. Richer, an astronomer at the University of British Columbia, said the Hubble Space Telescope gathered images of the faintest dying stars it could find in M4, a star cluster some 7,000 light years away.

Richer said the fading stars, called white dwarfs, are actually burnt out coals of stars that were once up to eight times the size of the sun. After they exhausted their fuel, the stars collapsed into Earth-sized spheres of cooling embers that eventually will turn cold and wink out of sight.

Earlier studies had established the rate of cooling for these stars, said Richer. By looking at the very faintest and oldest white dwarfs possible, astronomers can use this cooling rate to estimate the age of the universe.

Speaking at a news conference Wednesday, Richer said the dimmest of the white dwarfs are about 12.7 billion years old, plus or minus about half a billion years.

Richer said it is estimated that star formation did not begin until about a billion years after the Big Bang. He said this means his best estimate for age of the universe is "about 13 billion years."

Three years ago, astronomers using another method estimated the age at 13 to 14 billion years. That was based on precise measurements of the rate at which galaxies are moving apart, an expansion that started with the Big Bang. They then back-calculated  like running a movie backward  to arrive at the age estimate.

"Our results are in very good agreement" with Richer's estimate, said Wendy L. Freedman, an astronomer at the Carnegie Observatories in Pasadena, Calif., and a leader of the group performing the universe age calculations three years ago.

Bruce Margon, an astronomer at the Space Telescope Science Institute, said both conclusions are based on "a lot of assumptions" but the fact that two independent methods arrived within 10 percent of the same answer is important.

"To find an independent way to measure the age and then get essentially the same answer is a fantastic advance," said Margon. It may not be the final answer for the universe's age, he said, but is "very, very, very close."

To get the new age estimate, the Hubble Space Telescope collected light from M4 for eight days over a 67-day period. Only then did the very faintest of the white dwarfs become visible.

"These are the coolest white dwarf stars that we know about in the universe," said Richer. "These stars get cooler and cooler and less luminous as they age."

He added: "We think we have seen the faintest ones. If we haven't, then we'll have to rethink" the conclusions.

The faintest of the white dwarfs are less than one-billionth the apparent brightness of the dimmest stars visible to the naked eye.

M4 is a globular cluster, thought to be the first group of stars that formed in the Milky Way galaxy, the home galaxy for the sun, early in the history of the universe. There are about 150 globular clusters in the Milky Way; M4 was selected because it is closest to Earth.

The new age estimate for the universe is the latest in a long series of attempts to measure the passage of time since the Big Bang. Edwin Hubble, the famed astronomer who first proved that the universe is uniformly expanding, estimated in 1928 that the universe was two billion years old.

Later studies, using the very expansion that Hubble discovered, arrived at an estimate of about nine billion years for the universe age. This created a paradox for astronomers because some stars were known to be more ancient and it is impossible for stellar bodies to be older than the universe where they formed.

Freedman and others then determined, using proven values for the brightness and distance of certain stars, that the universe throughout its history has not expanded at a constant rate. Instead, the separation of galaxies is actually accelerating, pushed by a poorly understood force known as "dark energy." By adding in calculations for this mysterious force, the Freedman group arrived at the estimate of 13 to 14 billion years.

What you are seeing is lots of estimation rather than contradiction. As more measurements are made, the results seem to be in better agreement. There should be error indicators with each estimate, if not, it's sloppy reporting.

Just two weeks ago astronomers announced they had discovered the oldest galactic cluster yet, 13.5 billion light years distant. It took at least a billion years for such clusters to form after the Big Bang, putting the age of the Universe at no less than about 15 billion years old. But I do love these contradictions!

It is only a contradiction if you ignore the measurement errors in BOTH. We already know the WHite dwarf methodology has an acknowledged error of 0.5 billion years. We don't know the error estimate for the observation in your linked article because it does mention it, but let's use 5% as a round number.

Taking the White dwarf estimate to it's upper most value (13.7 billion + 0.5 billion) yeilds 14.2 billion years. Taking your estimate of 15 billion years and using the minimum value based on a 5% measurement error, yeilds 14 and a quarter billion years.

My understanding is that the acceleration rates in most models have different epochs, with plateus and peaks, rather than being a constant or exponential acceleration. There are more than a few distinctly different epoch models, as far as I know.

I'll have to defer to "Physicist" and ThinkPlease" on details such as those....

There are two articles on yesterday's thread. "Galaxy clusters consist of thousands of galaxies gravitationally bound into huge structures," said Joseph Mohr, a professor of astronomy at the University of Illinois. "Because of the expansion of the universe, the clusters appear denser at larger redshifts, when the universe was younger and denser."

and from the other article . . .

Inside a gravastar, space-time would be "totally warped," the researchers say. Further, the inner space would exert an outward force, which would enhance the durability of the bubble

and . . .

Mottola and Mazur have taken their extreme idea to a mentally dizzying new level: The say our entire universe may be the interior of a giant gravastar.

For some reason these two articles together got my brain lobes flapping.

As I read the article (dated 25-November-1999), he only proved that it was possible. But I seem to recall some time in 2000 they made more careful measurements of the flatness of space and proved the universe was open-ended and not destined for a big crunch.

Maybe it's me, but what I see is lots of potentially out-of-date estimates, and NO scholarly references to back them up.

If I were so inclined, I could put up a website that said the Universe is 13 days old, and it would have as much validity on your list as any other internet website estimate.

Also, you fail to note the error range for each estimate. As I pointed out earlier on this thread, 20 years ago, they thought the Universe was 10-20 billion years old (or 15 +/- 5 billion, if you prefer). Today, they think it is 13.7 +/- 0.5 billion years old. There's no contradiction; the later measurement lies entirely within the earlier estimate.

Lot of information there to absorb, but real interesting. If the universe is inside a gravastar, what's outside the gravastar? Is that sitting in a universe of its own? Some of these theories may not be as extreme as they sound. I think anything's possible.

No doubt about it, as long as these methodoligies are accurate and repeatable.

Exactly; and if there were evidence that these methodologies were erroneous, you'd have posted it by now.

Lacking any evidence that they are erroneous, we conclude this is the best estimate we have, and our confidence in it is much greater than before we had this independent methodology that produces virtually the same answer.

So it can be measured that the universe ends 13 billion light years away? It isn't possible that there are stars way beyond what we can see? If this is the case, I stand corrected for anything I've said.

In the press conference Wednesday, they described their methodology as using exposures of such long duration that had their been fainter dwarfs, they would have been detected. In other words, the minimum detectable magnitude was below that of the faintest dwarf they saw, sufficiently lower such that they feel confident that they would have seen them if there were fainter ones.

The new Hubble camera is MUCH more sensitive, and they plan to use it to look for much fainter dwarfs (to verify that what they found WAS the faintest (and thus oldest), and to look at dwarfs in a completely differnt type of cluster, and in cluster much more distant.

There are interval estimates and there are point estimates. The two groups' point estimates disagree by about two billion years. Richer said himself his best guess was 13 billion years.

I'm not sure about the error in either of these studies. I've never heard of the 5% standard you cite. For this article, they seem to be using .5 billion ly vs. 5%. But you're definitely right about the contradiction thingy; i.e., I should've said discrepancy instead of contradiction because even if the interval estimates do not overlap we wouldn't necessarily have a contradiction in the strict sense of the word.

How faint would a dwarf have to be for the universe to be 20 billion years old? Really really faint, I guess. :)

They apparently are running at the edge of the sensitivity of the old Hubble scope equipment; this is why they selected M4 -- they just didn't have enough sensitivity to see dwarfs that old any farther away that M4 is.

I guess they are relying on image processing algorithms. If the light from the bright dwarves is subtracted from the light of the faint dwarves, large areas of image (larger than the bright dwarves alone) would become unusable. I think it wouldn't necessarily work too well if the faintest dwarves are in the center of the cluster, and it would be less effective for a larger cluster, otherwise the larger cluster could give better results.

Knowing the age of the universe is important, if there actually is an age to it. More importantly however, I think the question, where did if come from, and where does it end, or does it? Lets say we know for a fact, that the Universe is exactly 13 billion years, 9 months, 13 days, 6hours, 2 minutes and 16 seconds old.

This will still not tell us how the universe got here. It may help in the investigation, but it will not tell us the important question of, where did it come from?

Pascal trembled at the immensity of the universe and saw no point apart from God. Modern scientists can guess all they want (and who can disprove their claims...after all, no one who existed x-billion years ago is here to disprove them).

The next thing I want to hear from a scientist is that, after having seen the immensity of the universe, they fell on their faces before the Living God who WAS there whenever earth was created.

I think part of the problem is how does one measure time? Does time run at the same rate now as it did when the universe was first created? We already know time is relative concept, not a constant. We also know that time is warped around mass and progressively slows the greater a mass is. When scientists talk billions of years of time and try to relate it to our time in this solar system there could be huge discrepancies and numerous paradoxes.

It's evident that this method is better suited for setting a lower limit on the age, given all the standard physics assumptions, than an upper limit. I'm still skeptical of the "found the faintest one" concept. I'm not even so sure that clusters weren't produced until a fairly long time after the "big bang", or that light isn't reddening due to the expansion of space beyond the effect of recession. Obviously, if the rate of expansion and recession were the same, it wouldn't have been much of a bang.

Could it even be possible to discover galaxies 100 billion or more light years away?

I's possible, yes. But two preconditions would have to be met: (1) such galaxies would have had to exist 100 billion years ago; because (2) the universe would have to be at least 100 billion years old, so that the light from such galaxies would have had time to get to us.

I don't. Assuming the error estimates were done honestly, they will not all overlap. Statistically, we would expect approximately 2/3 of all measurements to include the correct value, and 1/3 of the measurements not to. Do a weighted average of the independent numbers, and then do a chi-squared. You might find that the agreement between them is suspiciously good.

Yes I understand the difference between measurement and theory, but the scientists are only measuring what they can see. Do you think it's posssible the universe bends at some point, like a road meaning that stars and galaxies go on forever, but we can't detect them? If the universe stops where the last stars we see about 13+ billion light years away, then we must be contained in something would you agree, similar to the gravastar theory?

I don't think that's the case, I think space is eternity. But anything's possible, which is why I'm skeptical of claims like the ones being made in this article. There's too much to know yet before drawing these sorts of conclusions.

Do you think it's posssible the universe bends at some point, like a road meaning that stars and galaxies go on forever, but we can't detect them?

The universe does bend, but unlike a road, the light bends along with it.

If the universe stops where the last stars we see about 13+ billion light years away, then we must be contained in something would you agree, similar to the gravastar theory?

The universe does not have a boundary. If you think in two dimensions, for a moment, it could be akin to the surface of the Earth: there could be a finite amount of space, but you could travel infinitely in any direction, if you wanted to.

I don't think that's the case, I think space is eternity.

Space may or may not be infinite, but in the first place, the amount of "stuff" we can in principle travel to (which is what I mean when I talk about the "universe") is demonstrably finite, and the "stuff" we can see is of finite age. Look out into the universe, and you see that it was a very different place 10 billion years ago.

But anything's possible,

That's just it. Some things are possible, but not just anything. At its core, the universe behaves according to one set of universal laws. Even in the complete absence of theory, our measurements have constrained pretty severely what those laws might be. We don't know nothing.

There are things going on in space that sometimes defy natural law, they occur when all conventional wisdom says that they should not be. Here's an example of what I'm trying to say.

Don't be fooled by the overblown rhetoric of a journalist. Physicists are always waiting expectantly for the latest violation of muon g-2. If you read the FR discussions here and here, you'll find my explanations of the significance of muon g-2 violation, and why we expect such violations to appear.

The muon g-2 result hardly turns physics on its head. We've always known that the standard model of particle physics is incomplete. What the measurement does is pare down the myriad extensions to the standard model that are floating around out there. At most one of those theories is correct. In any case, is highly unlikely that the correct model will overthrow much of what we already believe we know about particle physics.

So space itself is most likely infinite, only the particles that lie within it, like stars and planets are finite, approximately 13 to 15 billion light years away?? So if a galaxy lies 100 or more billion light years away, despite the distance with our technology of today we would still be able to detect it?

You are kidding, right? If not, just go to google.com, type in the following, and press [Google Search]. That should give you plenty of contradictory reading material.

Sorry, but I do not concider the internet to be the definitive research tool. Anyone can put up a webpage proporting any wacko idea/theory on any subject. Try your local library, in the physical science section. Newcats

We may never be able to detect it. If the universe (defined not as all the matter we can travel to, but all the matter that exists) is infinite in extent, then--except for our local bubble--all of it is receding from us faster than the speed of light. We can never reach it, and its light can never reach us.

That's not to say that we can now see everything we could eventually see, if we last long enough. Some galaxies that are just beyond our current horizon will eventually be visible; we can't see them now because (as far as we can see in our reference frame) they haven't formed, yet. We can in principle watch the process of star and galaxy formation in the early universe, as the universe evolves. As the universe expands, however, the recession velocity of the earliest observable universe increases, and time dilation dictates that it evolve ever more slowly, as the velocity asymptotically approaches the speed of light. That puts a strict outer limit on the matter we'll ever be able to see.

What? You're accusing the supernaturalists of hostility? At least there was no attempted thread hijacking this time.I have seen less of that since the religion forum has been provided.That makes me wonder, do the science minded go there to argue or attempt thread hijackings?

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